1. FIELD OF THE INVENTION
The present invention relates to a disk cartridge in which a double-sided disk is housed, and particularly to shutter device for opening and closing head entry apertures formed on both surfaces of the disk cartridge.
2. DESCRIPTION OF THE PRIOR ART
In terms of the ease of handling and protection from dust, disk recording media, such as magnetic disk and optical disk, are loaded to a recording and reproduction apparatus with the disk being still housed in a disk cartridge to accomplish the recording and reproduction of information. Therefore, a cartridge case that is the main body of a disk cartridge is provided with a head entry aperture so that the head can be brought into contact with the disk recording medium when the cartridge is loaded to a recording and reproduction apparatus. However, when a head entry aperture is provided in this manner, some disadvantages occur. For example, when the disk cartridge is not used, dust enters the cartridge case through this head entry aperture and adheres to the recording surface of the disk recording medium. In another instance, during the handling of a disk cartridge, a finger tapperedly comes into contact with the recording surface of the disk cartridge through this head entry aperture, thus contaminating the recording surface with the dust or damaging it. As a result, good recording and reproduction become impossible. For this reason, a disk cartridge is usually provided with a shutter that closes the head entry aperture if the disk cartridge is not used.
FIGS. 17a and 17b are plan views illustrating an example of such conventional disk cartridge (for example, Japanese Patent laid-Open No. 38388/82). FIG. 17a shows the front surface side and FIG. 17b the reverse surface side. The reference numeral 1 denotes a cartridge casing, 2 an upper casing, 3 a lower casing, 4 a disk recording medium, 5A and 5B a spindle holes, 6A and 6B a head entry aperture, 7 a shutter, 7A and 7B shutter surfaces, and 8A and 8B an openings.
In the figures, the cartridge casing 1 is composed of the upper casing 2 and the lower casing 3 which are internally incorporated with each other and the double-sides disk recording medium 4 is housed in it. The spindle hole 5 of the same diameter are provided almost in the center of each of the upper casing 2 and lower casing 3 coaxial with the disk recording medium 4. Furthermore, on the forward side (upper side of the figures) with respect to the spindle holes 5 of the upper casing 2 and lower casing 3, the head entry apertures 6A and 6B of the same shape are formed in a manner that they readily cross the whole recording area of the disk recording medium 4 and they are superposed on each other.
The U-like shutter 7 is installed on this cartridge casing 1 in a manner that the cartridge casing is sandwiched between both sides of the shutter 7. The opening 8A is found in the shutter surface 7A of the upper casing 2 of this shutter 7 (FIG. 17a) on the right side from the center as viewed in the figure. The opening 8B is formed in the shutter surface 7B of the lower casing 3 of this shutter 7 (FIG. 17b) on the left side from the center as viewed in the figure. These openings 8A and 8B are arranged so that they are superposed with each other; the openings 8A and 8B have almost the same shape as the head entry apertures 6A and 6B and are a little larger than the head entry apertures 6A and 6B.
This shutter 7 is slidable in the directions indicated by the arrows A and B with respect to the cartridge casing 1.
When this disk cartridge is not used, the shutter 7 is urged to one end of the slidable range, as shown in the figure, whereby the head entry apertures 6A and 6B are closed. However, when this disk cartridge is to be used, the shutter 7 is moved in the direction indicated by the arrow A and is urged to the other end of the slidable range. As a result, the opening 8A of the shutter 7 is set in a position including the head entry aperture 6A of the upper casing 2 and the opening 8B is set in a position including the head entry aperture 6B of the lower case 3, whereby the head entry apertures 6A and 6B open. When this disk cartridge 1 is inserted in a recording and reproduction apparatus after that, the head comes into contact with one of the two recording surfaces of the disk recording medium 4 through either of the head entry apertures 6A and 6B and the pad comes into contact with the other recording surface through the other head entry aperture. A spindle is inserted through the spindle hole 5A or 5B to receive the disk recording medium 4 thereon. When the disk cartridge 1 is to be taken out of the recording and reproduction apparatus, the head entry apertures 6A and 6B can be closed by moving the shutter 7 in the direction indicated by the arrow B.
Incidentally, in a disk cartridge of the above-mentioned construction, the shutter 7 is adapted to be moved only in the direction indicated by the arrow A with respect to the cartridge casing 1 in order to open the head entry apertures 6A and 6B. Therefore, if the disk cartridge is used with the upper casing 2 shown in FIG. 7a facing upward and information is to be recorded or reproduced with the other surface of the disk recording medium 4, the shutter 7 must be moved in the direction indicated by the arrow A in order to open the head entry aperture A because the shutter rests at the right end of the slidable area. In contrast, if the recording or reproduction of information is to be conducted with the other recording surface of the disk recording medium 4, the disk cartridge is on the side reverse to the condition shown in FIG. 17a and is used with the lower casing 3 facing upward and the shutter 7 rests at the right end of the slidable range as shown in the figure; therefore, the shutter 7 must be moved in the direction indicated by the arrow A in order to open the head entry aperture 6B. In this case, the direction indicated by the arrow A in FIG. 17b is opposite to the direction indicated by the arrow A in FIG. 17a as viewed from the recording and reproduction apparatus.
As is apparent from the foregoing, when this type of cartridge is used, the moving direction of the shutter 7 in the recording and reproduction apparatus must be changed depending on which recording surface of the disk recording medium 4 is used to record or reproduce information and the necessity of two sets of shutter moving mechanisms makes the construction of the recording and reproduction complex.
To cope with this problem, it has been proposed in Japanese Patent Laid-Open No. 43279/85, to provide a disk cartridge in which the shutter is moved only in one direction to open a head entry aperture in a recording and reproduction apparatus even when information is recorded or reproduced using either of the recording surfaces of a disk recording medium.
FIGS. 18a and 18b are plan views illustrating this disk cartridge disclosed in Japanese Patent Laid-Open No. 43279/85. FIG. 18a shows the front surface side and FIG. 18b the reverse surface side. The same reference characters are given to the parts corresponding to those shown in FIGS. 17a and 17b.
The shutter 7 of this disk cartridge has a form of the letter U and is attached in a manner that the cartridge casing 1 is sandwiched by it. However, neither the shutter surface 7A nor the shutter surface 7B has opening and the shutter surfaces are rectangular and large enough to sufficiently cover the head entry apertures 6A and 6B and the spindle holes 5A and 5B. This shutter 7 is slidable along a guide groove 9A and a guide groove 9B made in the upper casing 2 and lower casing 3 of the cartridge casing 1, respectively. However, when the disk cartridge is not used, the shutter 7 is in the middle of the width direction of the cartridge casing 1 and is pressed by a spring 10A and a spring 10B so that the spindle holes 5A and 5B and the head entry apertures 10A and 10B are all closed.
When the disk cartridge is used with the upper casing 2 in FIG. 18a facing upward and information is recorded or reproduced with one of the two recording surfaces of the disk recording medium 4, the shutter 7 is moved against the urging force of the spring 10 by means of a shutter moving mechanism not shown in the figure in the direction indicated by the arrow A up to the end of the slidable range. As a result, the spindle hole 5A and the head entry aperture 6A are opened. At this time, on the reverse side (i.e., the side of the lower casing 3) of the disk cartridge shown in FIG. 18b, the shutter 7 moves in the direction indicated by the arrow B with respect to the lower casing 3 and the spindle hole 5B and the head entry aperture 6B are also opened.
When information is recording or reproduced on the recording surface of the disk recording medium 4 on the reverse side of the above-mentioned recording surface, the disk cartridge is used with the lower casing 3 facing upward as shown in FIG. 18b. In this case, the spindle hole 5B and the head entry aperture 6B are opened by moving the shutter 7 against the urging force of the spring 10A (FIG. 18a) in the direction indicated by the arrow A (this direction being the same direction as indicated by the arrow A in FIG. 18a with respect to the recording and reproduction apparatus). At this time, on the front surface side (i.e., the side of the upper case 7) of the disk cartridge shown in FIG. 18a, the shutter 7 has moved in the direction indicated by the arrow B with respect to the upper casing 2 and the spindle hole 5A and the head entry aperture 6A are also opened.
As will be understood from the foregoing, in the disk cartridge of the above-mentioned construction, the shutter 7 is moved only in one direction when information is recorded or reproduced with both of the recording surfaces of the disk recording medium 4. Therefore, the shutter moving mechanism is simplified and the construction of the recording and reproduction is simple. Furthermore, it is possible to substantially prevent dust from entering the spindle holes 5A and 5B.
When the above-mentioned disk cartridge proposed is used, it is necessary to move the shutter located in the middle of the slidable range up to its end in order to open the spindle holes and head entry apertures. In FIGS. 18a and 18b, therefore, the shutter moving mechanism is provided on a straight line between the spindle holes 5A and 5B and the head entry aperture 6A and 6B. Because the cartridge mechanism for moving the head, pad, etc. is also installed on this straight line, it is very difficult to arrange the shutter moving mechanism, and further this mechanism is complex and large.
Therefore, if both sides of the shutter are each provided with one engaging part that engages with a shutter moving mechanism in which the shutter surfaces 7A and 7B of the shutter 7 move in the reverse directions indicated by the arrows A and B with respect to each other and that do not cross the head entry apertures 6A and 6B in FIGS. 18a and 18b and if the shutter 7 is pushed or pulled in the direction indicated by the arrow A in these engaging parts, it is possible to arrange one shutter moving mechanism sufficiently apart from the straight line between the spindle holes 5A and 5B and the head entry apertures 6A and 6B of the disk cartridge.
However, the shutter 7 is very thin. Furthermore, the rigidity of the shutter 7 is very low because it is usually made of plastic from the standpoint of fabrication and cost. Therefore, the mechanical strength of the above-mentioned engaging parts is very low. For this reason, the engaging parts may sometimes be bent when the shutter 7 is to be moved by pushing the ends of the engaging parts. Especially, because the shutter surface 7A and 7B are very narrow, the shutter 7 rattles greatly if there are backlashes between the guide grooves 9A and 9B and the engaging parts (not shown in the figures) of the shutter 7 which engage with these guide grooves. As a result, the engaging parts are easily bent and it becomes impossible to move the shutter 7 smoothly.